THE CAPTOPRIL TEST IN THE DIAGNOSIS OF RE NAL-ARTERY STENOSIS - SIGNIFICANT CHANGES IN-ACTIVE RENIN CONCENTRATION

The aim of this study was to demonstrate the diagnostic value of chang es in active renin concentration during the captopril test (measuremen ts of plasmatic active renin concentrations, before 12.5 or 37.5 mg of captopril p.o., and 30 and 90 minutes after) in order to screen a sig nificant renal artery stenosis. After a renal angiography, 88 hyperten sive patients suspected of renovascular hypertension were classified a ccording to the percentage of stenosis in the main renal artery : clas s I (< 30 % - n = 50), II (30 to < 75 % - n = 2 1), III (75 to < 90 % - n = 8) and IV (90 to 100 % - n = 11). The results of the captopril t est were compared to those of renal angiography. The active renin befo re the test (basal AR), the greater increase in active renin after cap topril (max AR), the difference between max AR and basal AR (DIF) and the active renin relative change after the test (RC) were compared in the 4 classes (ANOVA). There were no differences in diastolic blood pr esure (greater-than-or-equal-to 90 mmHg) natriuresis (100 mmol/24 h in mean) between these different classes. The basal AR, the max AR, the DIF and the RC significantly differed between the 4 classes.They were greater in class III and IV than in class I. The positive criteria for the captopril test were max AR, DIF and RC. The positivity thresholds were max AR greater-than-or-equal-to 70 ng/l, DIF greater-than-or-equ al-to 50 ng/l and RC greater-than-or-equal-to 165 % (upper limit in th e class I 95 % confidence interval for each criterion). In this study captopril test sensitivity was 68,4 %, specificity 88 %, the positive predictive value 60 % and the negative predictive value 98 %.